A dynamic range is an important factor for indicating the image quality of an image sensor. A dynamic range generally represents the maximum range in which an input signal is processed without causing distortion. As the dynamic range of the image sensor is wider, a better image may be obtained without a brightness change of a wide range.
However, due to a narrow dynamic range, the related art color image sensor has a limitation that original colors thereof are not well represented, when any one or more of red, green and blue colors are saturated. In order to overcome the limitation of the narrow dynamic range, schemes of implementing wide dynamic range (WDR) pixels are suggested.
For example, a capacitor can be added to change floating diffusion (FD) capacity, and a transistor for controlling the added capacitor can also be added.
Alternatively, two independent photo diodes (PDs) can be included in a single pixel.
However, the above described schemes result in a large chip size and a complicated process by adding the capacitor or the PDs.